Practice question

Dictyostelium discoideum aggregation forms multicellular slug that later differentiates into prestalk and prespore zones. Extracellular cAMP serves dual role chemotactic signal and morphogen; within slug tip, high cAMP concentration suppresses prestalk differentiation while promoting prespore fate via activation of cAMP-dependent protein kinase and transcription factors. Prestalk cells preferentially arise at anterior where low extracellular cAMP and higher DIF-1 prevail. Experimental addition of high exogenous cAMP converts cells toward prespore lineage expressing spore coat proteins. Thus high extracellular cAMP milieu, not low, drives prespore formation, contrasting with low cAMP favoring stalk during culmination and ensuring proper proportioning.